The effect of antifreeze proteins on the cold tolerance of goldfish (Carassius auratus L.)

The antifreeze proteins (AFP ) and glycoproteins (AFGP) of high latitude marine teleosts are an adaptation to extreme low temperature in the presence of ice. Through their affinity to ice crystals, antifreeze proteins are able to adsorb to the surface of ice crystals and prevent their growth. In this way, fish producing them are able to live at temperatures one or more degrees below their plasma freezing point without freezing. -- Recent studies point to the possibility that antifreeze proteins may play a role in the nonfreezing cold adaptation of the fish producing them. To test the ability of antifreeze proteins to increase the cold tolerance of fish, warm-acclimated goldfish were injected with antifreeze proteins and exposed to various nonfreezing low temperatures. All three antifreeze types tested (Type I AFP from winter flounder, Type III AFP from ocean pout, and AFGP from Atlantic cod) increased the cold tolerance of goldfish as evidenced by the proportion of antifreeze-injected fish recovering from cold narcosis or cold coma. The AF(G)Ps did not increase the amount of time goldfish could remain exposed to a test temperature before the onset of cold coma, nor did they decrease the temperature at which narcosis occurred when temperature was lowered gradually. These results suggest that antifreeze proteins prevent or reduce cell damage arising from cold shock at rapidly reduced temperatures. The results of this study, along with those of previous studies, suggest a role for antifreeze proteins in nonfreezing cold tolerance and have implications for cold water aquaculture.